Method of making a focus anode



Feb. 1, 1966 J. H. JOHNSON 3,231,959

METHOD OF MAKING A FOCUS ANQDE Filed Sept. 5, 1962 2 Sheets-Sheet 1 I i I 3 I INVENTOR j )Z dkbzzsaz BY wed a li 1W ATTORNEYS Feb. 1, 1966 J. H. JOHNSON 3,

METHOD OF MAKING A FOCUS ANODE Filed Sept. 5, 1962 2 Sheets-Sheet 2 I INVENTOR BY (30L, v

ATTORNEYS United States Patent Ofiicc Patented Feb. 1, 1966 I 3,231,959 METHOD OF MAKINGA FOCUS ANODE Jay H. Johnson, Owenshoro, Ky., assignor to Kentucky Electronics, Inc., Owensboro, Ky., a corporation of Kentucky Filed Sept. 5, 1962, Ser. No. 221,600

1 Claim, (Cl. 29-2514) This invention relates to electron tubes and more particularly, to a method of making a focusing anode of an electron gun.

Priorly, numerous methods were employed to fabricate annular focusing anodes for electron guns. For example, one of the prior art methods of forming the focusing anode is to form a cup from strip material on an eyelet machine by a progressive die-drawing operation.

Next, the upper flange of the cup is trimmed to proper dimension and then the bottom of the cup is pierced to complete the annular ring. When the upper flange is trimmed, an outer lip is produced. The piercing of the end wall of the cup leaves a lip on the lower flange or opposite flange of the anode. These irregularities tend to prevent the proper beam-forming operation of the anode because they produce irregularities in the electrostatic field surrounding the anode Accordingly, it is an object of this invention topro vide an improved method for constructing electrodes for an electron tube.

It is another object of this invention to provide an improved construction of an annular ring anode for an electron tube.

Briefly, in accordance with aspects of this invention, I obviate the disadvantages of the prior artmethods of anode construction by forming a blank or starting with a fiat strip stock, edge rolling the stock to round the edges, cutting the stock in lengths corresponding or equal to the circumference of the anode to be formed and joining the ends of each length to form an annular ring. This novel method eliminates several unnecessary steps of the prior art method by eliminating the formation of lips on the edges of the annular ring.

It is sometimes desirable, or even necessary, to make the focus ring other than cylindrical. For example, it may be distorted to aslight elliptical cross section to control the cross section of the electron beam, or to.

compensate for some other distorting factor in the lens. The desired distortion of the ring is so slight as not to be visible, but is measurable by instruments well known in the art. With the novel method of this invention, the forming of elliptical cross sectioned focus rings is facilitated. In fact, it is possible to produce an elliptical cross section focus ring within the same close tolerances as are achieved in making the ring with a round cross section. Advantageously, the seam formed on the ring in performing this method maybe used as the point of reference accurately to identify the major or the minor axis of the ellipse. Such an arrangement facilitates orientation of the assembly in the electron gun.

These and various other objects and features of the invention will be more clearly understood from a reading of the detailed description of the invention in conjunction withthe drawing in which:

FIG. 1 is a view in section of an annular anode produced by the above described prior art method;

FIG. 2 is a View in plan of a portion of the stock to be employed in this novel method;

FIG. 3 is a view of the stock as it is pass ng between a pair of edge rollers; i

FIG. 4 is a view partly in section of the anode formed 1 by this novel method; and

FIGURE 5 is a view of an electron beam tube having an elliptical focus ring;

FIGURE 6 is a plan view in section of a mandrel form about which the focus ring is wrapped;

FIGURE 7 is a side View of the mandrel of FIG- URE 8.

Referring now to FIG. 1, there is depicted a view in section of an annular ring 10 formed by the prior art method described above. This ring has an outer lip 12 on one edge and an inner lip 14 on the opposite edge. The lip 12 is formed when this edge is trimmed. The lip 14 is for-med when the end wall of the cup is pierced to define an annular ring. In each instance, the flange must be subsequently machined to a very close tolerance. In addition, to the elimination of the lips 12 and 14, the

internal and external diameters of focus anodes must be held within close tolerances for the entire length of the ring and it has not been possible to maintain tolerances of i.0()l inch on both internal and external diameters for the entire length of the ring under the prior art.

The novel focus ring according to this invention remains within an out-of-around tolerance of i.001 inch both before and after firing (heat-treating to remove iinpurities and gas from the ring prior to assembly of the cathode ray tube) even when fired in a bulk container. The prior art focus rings are work-hardened and subjected to stresses by the repeated drawing and machining process. Unless they are individually stacked for firing, the hardening and stresses tend to be relieved unevenly and cause the rings to become misshapen. They cannot,

, the stock become rounded as shown to an enlarged scale in FIG. 3. The stock 29 is then cut to lengths equal to the circumference of the anode to be formed and notches may be formed in one end of the length of the stock and tongues formed in the opposite ends so that the notches and tongues may be joined together when the anode is wrapped around a suitable cylindrical form. As best seen in FIG. 4, the lengths of stock may be formed with tongues 26 on one end and notches 28 on the other end. When the strips or links 20 are wrapped around a cylindrical or elliptical mandrel form, as shown in FIGURES 6 and 7, are formed. This novel method provides an annular ring having an inner diame- I ter which can be closely controlled and the outer diameter of which can be held within tolerances of plus andminus of an inch, which tolerances could not be achieved by the prior art method,

The aforementioned elliptical focus ring in the lens for controlling the electron beam is visualized in the tube 39 of FIGURE 5. This shows the minor 4i) and major 41 axes of an elliptical focus anode 43 through which ispassed electron beam 42. The focus anode must be made and mounted very precisely to shape the beam 42, and is oriented about the seam 28, by means of mounting structure 33 as better shown in FIGURES 8 and 9.

embodiment of'this invention, it is understood that the concepts thereof might be employed in other embodiments without departing from the spirit and scope of this invention.

What is claimed is: 7

The method of forming an anode for an electron tube in an elliptical form oriented with the electron beam comprising the steps of rounding the edges of a piece of stock having a rectangular cross section, cutting said stock into lengths equal to the circumference of the anode to be formed Wrapping the lengthsaround an elliptical form, joining the ends of said lengths in a seam, referencing the axes of the ellipse relative to the seam, and orienting the assembly relative to the beam in an electron gun.

References Qited by the Examiner UNITED STATES PATENTS Kelsey 29-521 XR Hancox 8058 Klaus 29--534 Shaw et a1. 29521 Erdelyi 29-534 Budinger et al. 29521 XR Jones 29521 XR WHITMORE A. WILTZ, Primary Examiner.

J. F. CAMPBELL, Examiner.

15 J. D. HOBART, Assistant Examiner. 

